Pulse width modulation (PWM) may be used in a number of applications, such as motor control and switching regulator control applications, as just a few examples. A PWM signal typically is a periodic signal, which has two time segments in each period: an on time interval (called the “on time”) in which the PWM signal has a first state, or level (a logic one level, for example); and an off time interval (called the “off time”) in which the PWM signal has a second level (a logic zero level, for example). By regulating a ratio (called the “duty cycle”) of the duration of the on time to the period, the average, or DC, level of the PWM signal may be controlled for purposes of controlling an end device that responds to the PWM signal. For example, the duty cycle of a PWM signal may be regulated for purposes of controlling the speed of a DC motor.
For purposes of controlling more complex end devices, such as an AC synchronous electrical motor, a set of PWM signals (one for each winding of the motor, for example) may be employed. Depending on the application, the set of PWM signals may be edge-aligned or center-aligned PWM signals, a distinction based on the timing of the PWM signals relative to each other. For edge-aligned PWM signals, either on or off time boundaries of the PWM signals are aligned in time. For example, a set of edge-aligned PWM signals may have the beginnings of the respective off times aligned, although the duty cycles may vary among the PWM signals. For center-aligned PWM signals, either the on or off times of the PWM signals are symmetrical. For example, a set of center-aligned PWM signals may have the center points of their on times aligned, although the duty cycles may vary among the PWM signals.